Harahap, F. S.; Walida, H.; Rauf, A.; Arman, I.; Sudarijah, S.; Harahap, S. Study of Soil Properties on Various Slopes in the Cultivation of 15-Year-Old People’s Rubber Plants in Janji Village, Bilah Hulu District, Labuhanbatu Regency. ictess 2026, 1, 717-723.